Though this act of culinary defiance broke the school rules, he wasn't betraying any faith by gobbling pork-filled treats.

Sharp, now 30, was an atheist teenager and had atheist parents.

He had originally attended an Anglican boys' school, but got into trouble often and was eventually expelled.

His parents then chose The Emanuel School in Randwick simply because they thought he would be better off there than any of the other local schools.

''As soon as I went to Emanuel, because it was so small and there were girls there, I became more focused … it was a great school to go to,'' he says.

Having no religious conviction is increasingly common in Australia. A record 22 per cent of the country indicated as much in the 2011 census.

Yet the popularity of religious schools is increasing. Enrolments in independent and Catholic schools are growing faster than at public schools, increasing by about 1.8 per cent in 2012, compared with 1.2 per cent for public schools, according to recent data from the Australian Bureau of Statistics.

''It's one of the great paradoxes of Australian education,'' says Dr Helen Proctor, from the University of Sydney. ''We're one of the least-religious nations in the world, yet we have this large and increasing attendance of children in religious schools.''